For years, anyone buying or selling a home affected by Japanese knotweed ran into the so-called seven-metre rule. If knotweed was found within seven metres of a property, alarm bells rang, valuations were affected and sales stalled. In 2022 that changed, and it is worth understanding why, because it affects how your property is assessed today.
What was the 7-metre rule?
The seven-metre rule was a rule of thumb introduced in 2012 to help surveyors judge the risk knotweed posed to a building. In practice it was a blunt instrument. A House of Commons committee described it exactly that way, noting it did not reflect the actual behaviour of the plant and was causing unnecessary alarm.
What changed in 2022
A new RICS professional standard came into effect on 23 March 2022 and removed the rigid seven-metre measure. Instead of a single distance, surveyors now use their professional judgement to assess the genuine risk to a property. Where off-site knotweed is being considered, the distance of interest was reduced from seven metres to three metres.
The new risk categories
The updated approach sorts infestations into four risk categories, from A to D, reflecting the real impact on the property and its value rather than a crude distance. This gives lenders and buyers a much more nuanced picture, and it means many properties that would once have been red-flagged can now proceed normally.
What it means if you are selling
The change is good news, but it does not mean knotweed can be ignored. A professional survey and, where treatment is needed, a recognised management plan with an insurance-backed guarantee remain the key to a smooth sale. See our survey page for how we help.
What it means if you are buying
If a property you are interested in has knotweed, do not panic. Ask whether there is a management plan and guarantee in place. If there is not, that is something we can put right. Our residential service is built around exactly these situations.
Talk to a qualified surveyor
Our surveys follow current RICS guidance and are carried out by a PCA Certificated Surveyor. Call 07518 456090 or book a call-back.
